This invention pertains to a safety device for a heat exchange equipment filled with pressurized liquid, particularly a central heating installation, which safety device comprises a liquid tank, a pipe connecting said tank to the equipment to be protected, which pipe is divided in one location at least into two paths, which safety device comprises in the divided portion location, in the one path, a pump which can pump the liquid from the tank to the equipment and in series with said pump, a one-way valve which only lets liquid flow to the equipment and, in the other path, thus shunting said pump and one-way valve, an electro-magnetic valve, which safety device further comprises a contact manometer which connects to that pipe portion which lies between the equipment and on the one hand the electromagnetic valve in the one path and on the other hand the one-way valve in the other path, and which controls said pump and said electro-magnetic valve in such a way that when the pressure drops below a determined value, the pump starts operating and when the pressure rises above a determined value which is at least as high as the preceding value, the electromagnetic valve opens.
Such devices are notably used in central heating installations, mostly for balancing the water contraction and expansion due to temperature changes. Said safety devices are generally chosen rather than a safety device which only comprises an open tank which is mounted at the highest level of the heating installation. Said tank is not only located far away from the heating boiler proper which is cumbersome, but also the water inside the tank is continuously contacting air in such a way that oxygen can be absorbed which promotes the corrosion in the heating installation.
In known safety devices of the type concerned here, whereby thus a contact manometer, a pump and an electro-magnetic valve are provided, the tank is a pressurized closed tank. Inside said tank is present an amount pressurized nitrogen which is separated by a diaphragm from the water; said nitrogen is more or less pressurized depending on the water pressure. On said tank is mounted a safety valve for the case where the water pressure should rise too much, to let water escape from the tank. While such safety devices are very suitable in small heating installations, they are very expensive for very large heating installations, for example central heating installations in tower buildings or "sky-scrapers". Not only does the tank then have to be of a very large size, but also it is then required to work with a very high pressure, with the result that both the tank and the heating installation have to be of heavy construction. When it is desired in such known safety devices, to provide for an automatic filling-up when the liquid level inside the installation is too low, this also requires a very intricate and consequently very expensive control device.
The invention has for object to obviate the above drawbacks and to provide a safety device of the above-defined type which has a very simple structure and thus does not require any expensive pressurized tank and whereby the automatic filling-up of liquid in the equipment can be insured in a very simple way.